Determining Closing Speed in Rear Impact Collisions with Offset and Override

Considerable research has been dedicated to establishing the amount of energy absorbed during different types of collisions. In the early 1960’s, motor vehicle manufacturers began conducting barrier crash tests consistent with SAE suggested procedures. This allowed investigators to establish the amount of energy that went into metal deformation in the tested vehicle. Over the years, there have been many advances in establishing the amount of crush energy in a particular accident, including the development of several computer programs.

Four two-vehicle, single-moving rear-impact crash tests were conducted to compare the effect of override and offset. Override comparisons were made using a moving, rigid barrier or a heavy truck as the impactor, and each pair of tests having either offset or full rear engagement. All four tests were conducted using a like make and model four-door sedan as the target vehicle. Each test had the same available crush energy for the car. The vehicles were instrumented with triaxial accelerometers, and the tests were documented with high-speed film cameras. Crush profile information is presented to compare the damage generated by the truck and moving barrier. Analyses of the stiffness characteristics of the car in the two collision types are presented. This paper focuses on methods of establishing crush energy in override and offset collisions.